The invention relates to a method and device for presenting information, in a way that is easy for an operator, such as a pilot in an aircraft, to grasp and understand, concerning the direction to objects in the surrounding space. In accordance with the invention, the object is projected onto a surface comprised of the envelope surface of a conical solid of revolution, where the operator is somewhere vertically on the axis of rotation about which the envelope surface is created. Thereafter, the operator observes, on a display surface such as a viewing screen, a plan view from above of the conical envelope surface, where the horizontal direction to the objects, and the each object""s relative height are easily read.
It is a known fact that it is difficult to create a three dimensional image on a flat screen. It is, however, often necessary to provide an operator, a pilot in a plane for example, with information about what is happening in the surrounding air space. There are a number of solutions that use a flat screen to inform the operator about occurrences in the surroundings. A known example is a so-called PPI, which with the help of radar shows, on a flat screen, the distance and direction to a craft In this case, no information on the craft""s vertical position is provided, important information for an observer in an aircraft Another example is the case in which a pilot in a fighter aircraft receives information, through its own radar or other target seeker, on bearings and angle of altitude to foreign craft, whereby the craft is imaged as a point on a flat screen. The screen has both a horizontal and a vertical axes, whereby the position of the point to the right of the vertical axis gives the bearing of the craft to the right by up to 180xc2x0, while the position of the point to the left of the vertical axis corresponds to the bearing of the craft to the left by up to 180xc2x0. The position on the screen of these points along the vertical axis corresponds to the altitude of the craft, since the vertical axis represents a scale of altitude.
Commonly used nowadays, such a display on a screen may be difficult for a pilot to interpret A pilot, particularly the pilot in a fighter aircraft, has a range of instruments in his field of view, which means that in stressful situations interpretation of the instrument information on the displays must be easily accessible and easily convertible to one""s own conception of the world and of space.
The document U.S. Pat. No. 5,181,028 gives an example of a display for communicating information to a pilot on the position of nearby aircraft on a flat screen, where these are represented on a spherical grid transformed to a plane projection. However, it is complicated to use, as application requires the use of means to stereoscopically read the display.
One aspect of the invention is shown by the independent claims for the method and the device. In accordance with this aspect, it is shown how one technically creates an image of surrounding space and the direction to objects in space for display on a plane display surface, for example a viewing screen. The image of the surroundings is obtained by creating, about a reference positionxe2x80x94normally one""s own position, an imaginary projection surface in the form of a surface of revolution with a vertical axis of rotation, where the cross-section of the surface of revolution increases in the direction from one end of the axis of rotation to the other end. The height of the projection surface is arbitrary. In this description, the term cone is used to describe the surface of revolution, since the surface of revolution can be either jutting inwards or outwards. The reference position in space is on the axis of rotation, so that a horizontal plane through the reference position defines a circular curve on the projection surface, which shows the height of the reference position. The height of the reference position refers here to the height of the reference position in the body encompassed by the projection surface. On measuring an object for which one wants the direction shown on the projection surface, the position is determined for the point where a line of collimation from the reference position through the object intersects the projection surface.
It is now technically possible to image the direction to the object on the projection surface, i.e. normally an instrument window, by showing a plan view of the defined projection surface, which, for example, can be embodied by the aforementioned cone, across its axis of rotation. The display surface shows a largest circle that denotes the largest cross-section of the projection surface, and a circle that represents the height of the reference position projected on the projection surface. One""s own position is represented by the center of the circle, where the axis of rotation of the projection surface is located. This mid-point may be indicated by some kind of graphic symbol. From one""s own position, a reference direction, i.e. a zero direction, is defined on the circle defining the horizontal plane of the reference position.
Recording the object involves obtaining a direction to it, whereby by means of calculations, the position of the image of the object on the projection surface is determined, and is entered as a point on the plane image of the projection surface on the display surface. It follows that the said point, which is positioned on the line of collimation to the object, will represent the direction to the object as seen from the reference point. If the cone is positioned so that its base is oriented upwards and the point lies outside the horizontal circle representing the reference height, then the object is positioned higher than the reference position, i.e. the angle of altitude to the object is positive. If the point in this case is below the horizontal circle, then the object is positioned lower than the reference height, i.e the angle of altitude to the object is negative. Moreover, the angle with the apex at the mid-point from the reference direction to the line of collimation to the object represents the bearing of the object relative to the reference position. It is preferable for the bearing to be counted from the reference direction, 180xc2x0 to the right and 180xc2x0 to the left, thereby being intuitively in accord with one""s conception of space. For example, an object on an instrument window that is imaged as a point lying on the horizontal circle and 180xc2x0 to the right or left is, therefore, positioned in a direction that is directly behind and at the same height as the aircraft""s own position in the case where the reference direction signifies xe2x80x9cstraight aheadxe2x80x9d.
The reference height, i.e. the height of the circular curve displayed on the projection surface representing the horizontal plane of the reference position, may be either movable or fixed vertically on the projection surface. These versions illustrate two different applications of the technique. In the case where the reference height is fixed on the projection surface and the technique is used for a flying craft represented by the reference position, the projection surface follows the aircraft is fixed to it. In the other case, when the reference height is movable, the horizontal circle will move vertically on the projection surface in conjunction with any variation in the altitude of the aircraft. In the latter alternative, the circular curve, which shows the horizontal plane of the reference position on the projection surface, will rise as the aircraft ascends from lower to higher altitudes.
The described method and device can be used with advantage in aircraft to provide the operator, a pilot in this case, with an easily comprehensible orientation of the direction to the object, such as foreign craft in the surroundings, viewed from one""s own position, which in this case is the reference position. The pilot can obtain, in a way that is easy to grasp, angle information on these craft. This is a great advantage, since in this case a pilot has access to instrument systems in the aircraft that are based on angle measurements, such as different sensor systems, for example radar, IR sensors, and interception receivers. If the pilot is to perform a cognitive or motor action, where the action involves an angle-related maneuver, it is much easier if the action is supported by the method in accordance with the invention, since it only displays angles on the instrument window.
In accordance with the invention, the method and device can with advantage be used within any field where the relationships between object, occurrences and other phenomena can be described in accordance with the aspect of the invention, such as in military and civil aircraft, Air Force Headquarters, simulators, operational control, process control, and surveillance systems.